1. Field of the Invention
The present invention generally relates to an energy separating device, and particularly to a vortex type cold and hot gas separating device for separating a gas into cold and hot gas streams by using Ranque-Hilsch effect.
2. Description of the Related Art
Historically, the phenomenon of the Ranque-Hilsch effect is first found by Georges Ranque, a French metallurgical engineer, in 1930. At that time, Georges Ranque found in an experiment a vortex cooling effect in a cyclone separating device, i.e., a temperature at a center of a gas stream is different from temperatures of peripheral layers of the gas stream, the center of the gas stream has a lower temperature, while the outer edge of the gas stream has a higher temperature, in the cyclone separating device. According to this phenomenon, Georges Ranque subsequently designed a first vortex tube device which can separate energy in the history of mankind and filed a patent application in French in 1931. In 1933, Georges Ranque made a specific report about an experiment on the vortex tube device and its vortex separation effect of temperature in the French Physics Society. It is pointed out in the report that after a compressed gas with a temperature of 20° C. enters a vortex tube, a temperature of a cold gas stream flowing from the vortex tube is about −20 to −10° C. while a temperature of a hot gas stream flowing from the vortex tube can reach about 100° C., by the vortex separation effect of temperature. At that time, since a concept of a total temperature (stagnation temperature) of a fluid is confused with a concept of a static temperature of the fluid in Georges Ranque's expatiation upon a temperature separating phenomenon, the cold and hot gas separating phenomenon of the vortex tube was oppugned by scientists attending the meeting and generally negated in the meeting, finally resulting in interruption of further study on the vortex separation effect of temperature and the corresponding vortex tube device.
In 1945, Rudolph Hilsch, a German physicist, published a science report on the vortex tube which attracted the world's attention. In the science report, Rudolph Hilsch verified the vortex separation effect of temperature by using detailed material, and set forth a series of research findings and valuable advices for device design, application and a definition of temperature effect of the vortex tube. The vortex separation effect of temperature had not been formally accepted and acknowledged until then. Generally, the vortex separation effect of temperature is also named as the Ranque-Hilsch effect in memory of outstanding contributions of Georges Ranque and Rudolph Hilsch in this field.
So far, scientific research institutions, universities and enterprises of many countries have made a great deal of experiment research and theoretical explanation on the Ranque-Hilsch effect and a device for achieving it in the world. However, little progress has been made in both a basic theory and a device structure.
As shown in FIG. 1, a conventional vortex tube 10 is mainly composed of a nozzle 11, a vortex generating chamber 12, a vortex traveling tube (or called as a temperature separating tube) 13, a hot gas stream outlet 14, a cold gas stream outlet 15, and a vortex blocking and returning cone 16. According to a prevailing view in the prior art, when in operation, the vortex tube 10 jets a compressed gas into the vortex generating chamber 12 by an externally-disposed gas compressor (not shown in FIG. 1) through the nozzle 11; the gas jetted into the vortex generating chamber 12 first expands, and then enter the vortex traveling tube 13 at a very high speed in a tangent direction to travel in the form of a spiral vortex; and the traveling vortex is blocked by the vortex blocking and returning cone 16 before reaching the hot gas stream outlet 14, so that a portion of the gas stream will return in the form of a core vortex having a relatively smaller swirling diameter in an opposite direction, the unreturned gas is discharged through the hot gas stream outlet 14, and the returned gas is discharged through the cold gas stream outlet 15. Since the Ranque-Hilsch effect occurs in the gas in the vortex tube, a temperature of the gas of the outer-layer vortex discharged through the hot gas stream outlet 14 is higher than a temperature of the gas of the core vortex discharged from the cold gas stream outlet 15. Therefore, the gas stream discharged through the hot gas stream outlet 14 is named as a hot gas stream, and the gas stream discharged through the cold gas stream outlet 15 is named as a cold gas stream. Those skilled in the art could realize that the so-called hot and cold gas streams should not be limited to those having temperatures higher or lower than an absolute temperature value, but the gases flowing from the two gas stream outlets are defined relative to each other. In other words, concepts of the terms “hot gas stream” and “cold gas stream” are clear and definite in the art.
Although the vortex tube device is very simple in both structure and operation, an energy exchange process of the Ranque-Hilsch effect occurring in the device is extremely complicated. A heat transfer process is irreversible as a result of internal friction. Furthermore, the scientific community generally thinks that what the gas performs in the vortex tube device should be a complicated three-dimensional compressible turbulent flow. Therefore, so far, a mathematical model by which performance of the vortex tube device can be accurately predicted has been unable to be given in application of the Ranque-Hilsch effect. Explanations of the Ranque-Hilsch effect by the scientific community are also various, the scientific community has not yet set forth a very satisfying theoretical explanation of the Ranque-Hilsch effect, and even views of some theories themselves conflict with each other, in the basic theory. It can be said that theoretical research on the Ranque-Hilsch effect is a major problem currently confronted by the scientific community.
What is currently prevailing in the industry is a kinetic energy conversion theory with respect to cold and hot gas separation principles of the Ranque-Hilsch effect. The kinetic energy conversion theory is as follows.
The gas stream in the vortex tube device performs complicated motion. Specifically, the gas of the outer-layer vortex moves towards the hot gas stream outlet, the gas of the core vortex moves towards the cold gas stream outlet, the two vortexes rotate in the same direction, and it is particularly important for the two vortexes to rotate at the same angular velocity. Although there is violent turbulent flow in a boundary region between the gases of the two vortexes from the beginning to the end, the two vortexes can be regard as being integral from the point of view of rotational motion. The core vortex is enslaved to the outer-layer vortex. Therefore, the core vortex is a driven vortex, while the outer-layer vortex is a driving vortex. Water swirling flow generated in a bathtub is taken as an example to make a visual explanation. When discharging water, the water moves towards a core portion of an outlet and a rotational speed of the water will increase in order to conserve its angular momentum. A tangential linear velocity of particles in the water swirling flow is inversely proportional to a radius of the swirling flow. Therefore, when a radius of a driving vortex is reduced to a half as the particles in the water swirling flow move towards the core portion of the outlet, the tangential linear velocity, along the swirling, of the particles of the driving vortex is doubled, while the tangential linear velocity, along the swirling, of the particles of a driven vortex maintained at a certain rotational angular velocity is decreased by a half. The particles of the driving vortex flow into a sewage draining port at a linear velocity that is four times as large as that of the particles of the driven vortex. The kinetic energy is directly proportional to the square of the linear velocity. Therefore, in this example, the kinetic energy of the particles of the driven vortex which flow into the sewage draining port is only 1/16 of the kinetic energy of the particles of the driving vortex which flow into the sewage draining port. The prevailing conventional theory holds that the situation in the vortex tube in which the cold and hot gases are separated is similar to the above example. Where does a kinetic energy difference between the gas of the driven vortex and the gas of the driving vortex which totals to 15/16 of the available kinetic energy go? The conventional theory considers that this is just a key in exploration of the cold and hot gas separation principles in the Ranque-Hilsch effect, i.e., the kinetic energy difference will be transferred from the driven vortex in the core to the driving vortex in the outer layer in the form of heat. Thus, the gas of the driven vortex becomes the cold gas stream, while the gas of the driving vortex becomes the hot gas stream! The energy relationship between them is in accord with the law of conservation of heat and the law of conservation of energy.
Apparently, the above theory does not directly answer the question from microcosmic essence of a fluid temperature, but gives only a general explanation in a macroscopic aspect of the law of conservation of heat and the law of conservation of energy. Cognition on microcosmic essence of the Ranque-Hilsch effect is not deep. Hence, this also has led to the fact that all of the devices for achieving cold and hot gas separation by using Ranque-Hilsch effect have been limited to only the above-mentioned basic structure of the vortex tube for a long time. In addition, it is not clear with what geometric dimensional relationship of the structure in such basic structure a maximal difference between the temperatures of the cold and hot gas streams can be obtained. In other words, it is unclear with what geometric dimensional relationship an optimal cold and hot gas separation effect can be obtained. However, even for the basic structure of the conventional vortex tube, the number of design variables is up to at least 15, and each of the variables has infinite selections. Since influences of each variable and a relationship between the variables on an effect of the vortex tube are substantially all unknown or indefinite, the basic structure of the vortex tube device has not been improved much for a long time.
Particularly, the conventional vortex tube devices all demand that compressed gas having a very large pressure be used and require that the compressed gas be jetted into the vortex generating chamber 12 to expand at a high speed, then the gas expanding at the high speed enters the vortex traveling tube 13 having a smaller diameter to generate high-speed vortex, and finally the cold and hot gas separation be achieved by means of the Ranque-Hilsch effect. Under the guidance of the existing theory that is not clear enough, a person having ordinary skill in the art generally considers that in the vortex tube device, an inner diameter of the vortex traveling tube 13 should not be too larger since he is generally of the opinion that in order to obtain a maximal difference between the temperatures of the cold and hot gas streams, a ratio of a length of the vortex traveling tube 13 to the inner diameter (usually the ratio is also called as a length to diameter ratio of the vortex tube for short) should be larger, and further considers that the length to diameter ratio should be preferably larger than 10, and even larger than 45. In other words, in the state of prior art in the technical field, a person having ordinary skill in the art generally considers that the length of the vortex traveling tube 13 should be preferably longer, while the inner diameter of the vortex traveling tube 13 should be preferably smaller on such condition that the vortex can be generated and the return of the core vortex can be achieved.
In addition, the vortex tubes in the prior art generally all require that a gas compressor or a similar apparatus be used for supplying compressed gas. The vortex tubes are larger in assembled equipment, have a smaller output, and suffer from big limitation of an application field. Typically, a vortex tube on sale has a small diameter of around 30 mm and a length of around 300 mm so that its internal volume is very small. When in operation, compressed gas is jetted into the vortex tube at a speed close to the sound velocity such as a speed between Mach 1/3 and Mach 7/8. A nominal temperature of the vortex tube labeled by the manufacturer indicates that cold gas stream having an ultralow temperature of down to −60° C. can be separated by the vortex tube. However, the vortex tube device generates strident noise and has extremely high energy consumption when in operation since it requires that a great deal of compressed gas be used. It can be found through further research that since the internal volume of the vortex tube is very small, a phenomenon of sharp decompression, expansion, and temperature drop will occur in the compressed gas jetted from the nozzle when excessive gas enters the vortex tube. The phenomenon of decompression, expansion, and temperature drop is physically referred to as the Joule Thomson cooling process. The Joule Thomson cooling process does not have necessary direct relations with the Ranque-Hilsch effect, but in fact it is a main reason why this kind of devices obtain cold gas stream.
The inventor of the present application has creatively realized that the existing theoretical unknown has directly led to the following defects that generally exist in the existing vortex tubes for separating cold and hot gases:
1. it is necessary to use a gas compressor or a similar apparatus for supplying compressed gas having a large pressure, and sharp expansion itself of the compressed gas will cause temperature drop, loud noise, and low efficiency;
2. it is necessary to dispose a big vortex generating chamber for expansion of the compressed gas, and only a part of the gas can enter the vortex traveling tube in a tangent direction to form vortex, so that the efficiency is low;
3. the diameter of the vortex tube is too small and a gas disk of a swirling is too small, and time of a cold and hot gas separation process is too short, so that the cold and hot gas separating function cannot be brought into full play;
4. the vortex blocking and returning cone will generate a great deal of useless turbulent flow in a tail of the vortex traveling tube so as to reduce the efficiency of the device; and
5. the structure of the existing vortex tube device is not suitable for manufacturing a large vortex type cold and hot gas separating device, e.g. a vortex type cold and hot gas separating device with a large aperture (having a diameter more than hundreds of millimeters, for example) which has a large air quantity and a low wind speed.